Helical multistage flash distillation unit

ABSTRACT

A continuous, downwardly spiralling multistage flash evaporator passage. The condensing stages, one above the other, are provided in the core around which the evaporator passage winds.

United States Patent Webb 1451 Feb. 12, 1974 [54] HELICAL MULTISTAGE FLASH 1,804,554 5/1931 Dubbs 202/1511 x DISTILLATION UNIT 3,219,554 11/1965 Woodward 202/173 1 ,299,793 4/1919 Shaw 159/1 3 R Inventor: Richard Webb, Wflmington, 2,224,621 12/1940 Voorhees 203/89 [73] Assignee: The United States of America as represented by the Secretary of the FOREIGN PATENTS OR IP E H Interior, Washington, DC. 14,161 6/1911 matTtrifinlfiflifl.;... 159/13 A [22] Filed: Aug. 9, 1971 Primary Examiner-Norman Yudkoff [2!] Appl 173332 Assistant ExaminerDav id Edwards v V Attorney, Agent, or F irm-M. Howard Silverstein & [52] US. Cl 202/173, 203/11, 203/88, Erne t S, Cohen 203/89, 202/187, 202/236, 159/18 [51] Int. Cl B0ld 3/02, BOld 3/06 [58] Field of Search... 202/173, 226, 187, 174, 172, [57] ABSTRACT 202/158; 159/18, 13, 13 128; A continuous, downwardly spiralling multistage-flash 203/89 l 88 evaporator passage. The condensing stages, one above the other, are provided in the core around which the [56] References C'ted evaporator passage winds.

UNITED STATES PATENTS 3,503,853 3/1970 Taubert et a1. 159/18 R 2 Claims, 2 Drawing Figures SALINE WATER CONCENTRATED 1 BRINE PAIENIEDFEBIZ'W" Q's/919934 sum 1 0r 2 SAL! NE 5 WATER CONCENTRATED BRI NE //VVE/VTO/? RICHfl RD N. WEBB WWW ATTORNEYS PAIENIEBFEBIZW 3,791,934

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//vv/vr0/? I RICHARD IV. WEBB v ATTORNEYS HELICAL MULTISTAGE FLASH DISTILLATION UNIT The invention relates to the art of multistage flash distillation. It is well established that large quantities of distilland, particularly saline water, can be effectively purified in multistage flash distillation systems. As such, research is continuously being carried on to discover refinements, improvements or innovations in the system.

Toward these ends, the present invention involves a novel multistage flash system which includes a continuous, downwardly spiralling, substantially enclosed passage having a plurality of transverse partitions dividing the passage into a series of flash evaporator stages through which flashing distilland flows during its passage from the top to the bottom end of the passage. The central core around which the helical passage winds contains a condensing section divided into a series of condenser stages one above the other, each of which is in vapor communication with an adjacent flash stage in the helical passage.

It is therefore an object of the present invention to provide a compact multistage flash distillation system.

Another object is to provide a continuous downwardly spiralling distilland path.

A further object is to provide a distilland path winding downwardly around a vertically elongated condenser.

A still further object is to employ gravity and centrifugal force for rapid distilland movement through the flash stages.

Other objects and advantages will be obvious from the following more detailed description of the invention in conjunction with the drawings in which;

FIG. 1 is a fragmentary perspective view of the evaporator of the present invention, and

FIG. 2 is a fragmentary view of an evaporatorcondenser combination.

Referring to FIG. 1, numeral 1 designates the evapo rator of the present invention. A continuous, downwardly spiralling ramp 2 is provided within the evaporator ll. Inner wall 3 and outer wall 4 are contiguous to the inner and outer edges, respectively, of ramp 2, and thereby essentially enclose ramp 2 to define a continuous, downwardly spiralling, substantially enclosed passage. Superheated distilland, e.g., saline water, enters the top of the evaporator through feed conduit 5, and flashes as it flows along the ramp through the passage. Concentrated brine exits from the evaporator at conduit 6.

By suitably laterally and longitudinally sloping the ramp, centrifugal and gravitational effects can be used to spread the distilland liquid over a greater area and in a generally uniform depth, thus prompting better vapor release. Vortex breakers such as finger-like projections, extending from the floor or ceiling of the passage, can also be included to control distilland flow.

A series of transverse partitions P P P P divide the passage into a number of flash stages or compartments E E E E Although each stage is illustrated as occupying one full helical turn, each stage may be sized to occupy a number of turns or fraction thereof. Further, the size of each stage can vary from stage to stage, so that, for example, the first stage occupies 2 turns, the second stage occupies 1 turns, the third stage occupies 1 5 2 turns, etc. Such a progressive reduction in stage size can be employed to accommodate the progressive reduction in the volume of flashing brine during its downward travel through the helical passage.

Any of the well known means for providing vapor seals between adjacent flash stages can be employed in the evaporator of the present invention. As an example, weirs W W2, W3 w, are disposed adjacent to partitions p p p p respectively. Other vapor sealing devices include float controlled or otherwise adjustable orifices at the bottom of each partition.

Conduit means (not shown in FIG. 1) in either inner wall 3 or outer wall 4 provide vapor communication between an appropriate condenser and each flash stage.

In the preferred arrangement of the present invention as shown in FIG. 2, the condensing section 7 of the distillation unit is enclosed by inne wall 3. A plurality of vertically disposed elongated tubes 8 extend through section 7. Coolant such as cold saline water flows through these tubes from the bottom to the top thereof. A fluidized bed can be employed within the tubes, as for example the type employed in U. S. Pat. No. 3,476,655. Warmer water exiting from the top of the condenser tubes is further heated to a superheated condition in the prior art manner and then fed to the top of the evaporator.

A plurality of partitions D D divide condensing chamber 7 into a plurality of condenser stages C C C etc., one above the other, equal in number to the evaporator stages. Orifices 9 in inner wall 3 contact each evaporator stage with a respective adjacent condenser stage.

Pumps and conduits (not shown) are provided in the prior art manner to provide flashing pressures in each condenser stage, and to remove condensate and noncondensibles therefrom.

With regard to overall geometrical design, the apparatus of the present invention is such that, in crosssection, it defines a rounded object such as a circle or ellipse. Further, the apparatus can be somewhat tapered along its length to generally define an elongated cone in which the turns of the helical camp become wider toward the bottom. As used in the claims, the phrase generally cylindrical" in reference to inner and outer walls 3 and 4 is meant to include all these various shapes.

The combination sloping floor-spiral configuration design of the present invention accelerates distilland flow through the unit, and effectively increases stage length and the area available for vaporization without an excessive increase in overall plant area.

What is claimed is:

l. A multistage flash distillation comprising:

a. a continuous, downwardly spiralling, substantially enclosed passage winding around an elongated central core:

b. a plurality of transverse partitions in said passage depending downward from the roof of said passage and terminating above the floor of said passage, and dividing said passage into a series of flash evaporation stages; wherein said partitions are spaced progressively closer to one another from the uppermost to the lowermost end of said end of said spiral passage so that there is a progressive reduction in stage size from said uppermost to said lowermost end;

c. a weir adjacent to and downstream from each partition whereby liquid flows under each partition and over each weir and thereby provides a vapor seal between stages;

d. means to maintain said stages under progressively lower flashing pressure from said uppermost to said lowermost end of said passage;

e. means to feed superheated distilland to said uppermost end of said passage so that it may flow downwardly through said series of stages, and so that it may flash as it enters each of said stages;

f. a condensing chamber in said central core;

g. tube means extending through said chamber from the bottom to the top thereof; I

h. a plurality of horizontal partitions in said chamber dividing it into a plurality of condensing stages one above the other;

i. means to pass a condensing medium upwardly through said tube means; and

j. orifice means in said evaporator passage connecting each of said flash evaporation stages with an adjacent one of said condenser stages so that vapor evolved in each of said flash evaporation stages can pass into an adjacent condenser stage and condense upon said tube means.

2. The apparatus of claim 1 wherein said passage comprises a continuous, downwardly spiralling ramp; a first generally cylindrical wall contiguous to the inner edge of said ramp and defining said central core; a second generally cylindrical wall contiguous to the outer edge of said ramp, said first and second walls enclosing said ramp to define said substantially enclosed passage; and wherein said first cylindrical wall is provided with said orifice means which connect each of said evaporation stages with an adjacent condenser stage. 

1. A multistage flash distillation comprising: a. a continuous, downwardly spiralling, substantially enclosed passage winding around an elongated central core: b. a plurality of transverse partitions in said passage depending downward from the roof of said passage and terminating above the floor of said passage, and dividing said passage into a series of flash evaporation stages; wherein said partitions are spaced progressively closer to one another from the uppermost to the lowermost end of said end of said spiral passage so that there is a progressive reduction in stage size from said uppermost to said lowermost end; c. a weir adjacent to and downstream from each partition whereby liquid flows under each partition and over each weir and thereby provides a vapor seal between stages; d. means to maintain said stages under progressively lower flashing pressure from said uppermost to said lowermost end of said passage; e. means to feed superheated distilland to said uppermost end of said passage so that it may flow downwardly through said series of stages, and so that it may flash as it enters each of said stages; f. a condensing chamber in said central core; g. tube means extending through said chamber from the bottom to the top thereof; h. a plurality of horizontal partitions in said chamber dividing it into a plurality of condensing stages one above the other; i. means to pass a condensing medium upwardly through said tube means; and j. orifice means in said evaporator passage connecting each of said flash evaporation stages with an adjacent one of said condenser stages so that vapor evolved in each of said flash evaporation stages can pass into an adjacent condenser stage and condense upon said tube means.
 2. The apparatus of claim 1 wherein said passage comprises a continuous, downwardly spiralling ramp; a first generally cylindrical wall contiguous to the inner edge of said ramp and defining said central core; a second generally cylindrical wall contiguous to the outer edge of said ramp, said first and second walls enclosing said ramp to define said substantially enclosed passage; and wherein said first cylindrical wall is provided with said orifice means which connect each of said evaporation stages with an adjacent condenser stage. 